Parasitic worms afflict mammals and fowl and thus pose an economic problem in the raising of cattle, swine, poultry and fur-bearing mammals. A significant number of compounds containing an amidine structural feature have shown significant anthelmintic activity, e.g., levamisole, albendazole, thiabendazole, morantel and bunamidine. However, a compound that is active against one type of worm is not necessarily active against other types. Likewise, toxicity often varies from one host animal to the next. Therefore there is a need for new agents with activities against a broad spectrum of endoparasitic worms and with low toxicity toward the host.
Numerous isoxazoles, isoxazolines and isoxazolidines have been isolated from natural sources or synthesized, and individual compounds or closely-related groups of compounds have been reported to be active as herbicides, anti-protozoan drugs, hypoglycemic agents, anti-inflammatory agents, or anti-pyretic agents. It is obvious that having activity against one particular pest or biological dysfunction does not mean a compound will also be active against parasitic worms. In addition, the activity of a compound even against a single pest is almost impossible to predict from its structure. For example, two structurally similar compounds can have dramatically different anthelmintic activities, one being very effective and the other totally ineffective.